Unit 1- Protein Control of Cell Division Flashcards
Describe the cytoskeleton.
Gives shape and mechanical support to cells. Consists of microtubules.
What are microtubules?
Hollow, straight cylinders composed of tubulins. Radiate from the microtubule organising centre or centrosome.
Describe the cell cycle.
Interphase, Mitotic phase.
Describe the interphase.
G1- growth of proteins and organelles.
S - DNA is replicated.
G2 - further growth phase.
Describe the mitotic phase.
Mitosis (PMAT) AND cytokinesis.
Describe the prophase (PMAT).
DNA condensed into chromosomes each of 2 sister chromatids. Nuclear membrane breaks down. Spindle microtubules extend from MTOC and attach to kinetochores of centromere of chromosomes.
Describe the metaphase. (PMAT)
Chromosomes are aligned at the metaphase plate.
Describe the anaphase. (PMAT)
Spindle microtubules shorten by depolymerisation, chromatids are separated and chromosomes are pulled to opposite poles of the cell.
Describe the telophase. (PMAT)
The chromosomes condense and nuclear membranes form around them.
Describe cytokinesis.
Comes after mitosis, the cytoplasm is separated into two daughter cells.
What are checkpoints in the cell cycle?
Mechanisms which halt and assess the condition of the cell before progressing through cycle.
G1, G2, M.
Describe the role of cyclins and CDKs.
Cyclins combine and activate CDKs. Active CDKs phosphorylate proteins that regulate progression through the cell cycle. Sufficient phosphorylation allows progression.
What is retinoblastoma protein?
A tumour suppressor that inhibits the transcription of proteins needed for DNA replication. At the G1 checkpoint.
Describe the relationship between CDKs and Rb at the G1 checkpoint.
G1 CDKs phosphorylate the Rb. Phosphorylation inhibits Rb, allowing transcription of genes that code for proteins needed for DNA replication.
Describe the G2 checkpoint.
DNA replication and damage is assessed. DNA damage triggers activation of protein p53 which can: stimulate DNA repair, arrest cell cycle or induce apoptosis.
Describe the M checkpoint.
Progression is halted until the chromosomes are aligned on the metaphase plate and attached to spindle microtubules.
An uncontrolled reduction in cell cycle rate could cause what?
A degenerative disease, eg. Alzheimer’s.
An uncontrolled increase in cell cycle rate could cause what?
Tumour formation.
What is Proto-oncogene?
A gene involved in the control of cell growth or division which can mutate to form a tumour promoting oncogene.
Describe apoptosis.
Cell destruction triggered by external or internal death signals.
Describe external death signals.
Molecules bind to a surface receptor protein and trigger a protein cascade in the cytoplasm. Eg. Signals from lymphocytes.
Describe internal death signals.
A signal resulting from DNA damage causes activation of p53 protein.
